(1) Field of the Invention
The present invention relates to an image recording medium which is used in an electrophotographic process using a laser for toner fixing toner and toner removing and enables reuse of the image recording medium, an image recording medium reusing apparatus, an image forming apparatus including the same, and an image recoding medium reusing method.
(2) Description of the Prior Art
Lately, global environmental issues, in particular, the global warming problem resulting from emission of greenhouse gases, has caused a notably serious situation. In the field of image forming apparatuses such as copiers, printers etc., which use electrophotography, when the load on the environment of a product in the whole course of its life was evaluated by CO2 emission equivalent in Life Cycle Assessment (LCA), it turned out that the amount of CO2 arising in manufacturing image recording mediums (paper) that are consumed by the image forming apparatus is predominantly greater than the amount of CO2 generated at the time of manufacturing or disposal of the apparatus itself or the amount of CO2 corresponding to the electric power that is consumed by the apparatus itself. Accordingly, in order to sharply reduce the load on the environment from an image forming apparatus, reuse of paper is most effective.
From this viewpoint, various kinds of technologies for reusing sheets of paper that have been once image formed have been proposed.
Patent document 1 (Japanese Patent Application Laid-open H09-197926) discloses a technology of reusing the paper by separating the toner image from the paper by means of a heated separating member.
Patent document 2 (Japanese Patent Application Laid-open 2006-154485) discloses a technology of reusing the paper by erasing the shade of the toner image that has been formed using a toner that disappears when heated.
Patent document 3 (Japanese Patent Application Laid-open H01-101577) discloses a technology of reusing OHP film by removing the toner image from the film surface by immersing the toner on the OHP film in a toner resin-soluble solvent for a predetermined period to remove the toner image from the film surface.
Patent document 4 (Japanese Patent Application Laid-open H09-179461) discloses a technology of reusing the paper by applying a thermally fusible material to the toner image, heating and fusing the material with the tone image, pressing a releasing medium against the molten material and then parting the releasing medium from the paper to transfer the toner image with the thermally fusible material.
However, the above conventional reusing technologies suffer from the problems as follows.
That is, in the reusing technology described in patent document 1, a large amount of heat energy is needed when the toner is separated from the paper, hence this method is by no means preferable when the load on the environment is totally estimated. Further, the paper is thermally and mechanically damaged when the toner image is separated from the paper, hence this method also has the problem that the number of times of reusing is limited to several times.
In the reusing technology described in patent document 2, even if the shade of the toner image has been disappeared the toner resin still remains on the paper, so that it is impossible to make the image completely invisible. As a result, not only the number of times of reusing is limited but it is also undesirable in view of security. Further, since thermal energy is needed to erase the shade of the toner, this method is by no means preferable when the load on the environment is totally evaluated.
The reusing technology described in patent document 3 is aimed at OHP film. That is, the utility is limited. Further, since the toner resin may be made of polyester which is the same resin for forming OHP film, if this technology is used to deal with the toner resin of polyester, there occurs the problem that the film itself is also dissolved in the soluble solvent. Further, when the toner resin and OHP film are made of polyester resin, the toner presents a high affinity for OHP film. As a result, the fixing strength of the toner after fusing and fixing becomes very high, so that it is difficult to readily remove the toner image with the soluble solvent. In addition, the hydrophilic of the OHP film surface is high (the contact angle of polyester resin with water is 78°), and the soluble solvent that is based on water is ready to wet the film surface, so that there is also the problem that the solvent is consumed too much.
Further, the reusing technology described in patent document 4 has the problem that the thermally fusing material is consumed when erasing the image. Though the thermally fusing material does not contain any coloring agent like the conventional toner, it is also formed of toner material. Toner material in itself is expensive compared to the paper and produces CO2 when the toner is manufactured, hence it does not lead to reduction in environmental load. Further, this method needs separate heat sources for image recording and image erasing, resulting in a complicated configuration. Also, since the heat roller and the separating and heating roller have high heat capacities, it takes time to warm up the reusing apparatus. That is, it is necessary to always heat the apparatus beforehand for convenient handling, hence waste standby electricity is needed.